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Avalanche Forecast

Archived

Dec 15th, 2023–Dec 16th, 2023

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely.

Regions

Banff Yoho Kootenay, Little Yoho, Banff, East Side 93N, Kootenay, Lake Louise, LLSA, Sunshine, West Side 93N, Field.

Strong to Extreme southwest winds have generated some natural activity on the deep persistent layer and will remain elevated through Saturday.

Fresh wind slabs should be anticipated and can be expected to be sensitive to human traffic.

Travel remains poor BTL.

Days are short.

Practice conservative decision making.

Confidence

Moderate

Avalanche Summary

A large natural was observed today in the alpine on Mount Fairview. This was no likely a result of wind loading and failed next to the ground on the deep persistent layer.

Lake Louise ski patrol remote triggered a size 1.5 wind slab Thursday. The feature was at treeline and was a reloaded bed surface from a previous avalanche.

Snowpack Summary

Last week's storm snow has settled to 20-40cm at treeline. A rain crust up to 7cm thick exists within this storm snow as high as 2300 and has been found to be more extensive in the southern part of the region. Wind slabs are prevalent from previous strong winds.

This upper snow overlies the deep persistent weak layer that consists of surface hoar facets and depth hoar. Treeline snow depths range from 50-80cm.

Click here for the snow profile from Tuesday in the Dolomite peak area.

Weather Summary

SW alpine winds will increase into the extreme range Friday night.

Alpine temperature inversions look possible through to Monday morning as do trace amounts of snow.

Winds will shift W /NW and back off into the moderate range Sunday morning before shifting back SW and ramping right back up to strong range in the afternoon.

For more information, click Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Early season avalanches at any elevation have the potential to be particularly dangerous due to obstacles that are exposed or just below the surface.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.